A Study Of The Time Domain And Frequency Domain Signal Analysis Of Thermal Photoacoustic Imaging

Photoacoustic(PA) imaging is a new imaging technology that based on the photoacoustic effect. It combines the high contrast of optical imaging with the high penetration depth of ultrasound imaging. Photoacoustic imaging is the research focus in recent years. In this paper, we consider the effect of the excitation wavelength and the temperature to the photoacoustic, and study the thermral photoacoustic imaging using the time domain and frequency domain analysis method. This article mainly has carried on the following works:Firstiy, considering the influence of excitation wavelength, and in order to analysis the characteristics and differences of PA signal under different wavelengths in time domain and frequency domain, the multi-wavelength photoacoustic imaging experiment that used two different targets including PDMS phantom and pork fat was designed. The results proved that the performance of different targets was quite different in time domain and frequency domain. Especially, the acoustic spectrum of photoacoustic signal for different targets was unique. The frequencies corresponded to peaks of the acoustic spectrum were the same, so it is possible to be utilized for tissue characterization and component identification.Then taking the temperature factor into account, we propose a simple model of the relationship between photoacoustic signal and temperature and wavelength. Inorder to analysis the effect of the temperature and incident laser wavelength on photoacoustic imaging, two different samples including a PDMS phantom and a piece of pork blood were used for multispectral thermal photoacoustic experiments.The results showed that as the same temperature, when the laser wavelength was changed, the photoacoustic signal intensity of the phantom was different; when the wavelength was constant, the intensity of the photoacoustic signal changed with the temperature. The frequencies corresponded to peaks of the acoustic spectrum under different temperature were the same.Finally, on the basis of the above research, we use the frequency domain analysis method to study the influences on photoacoustic imaging of the microstructure of material. The results show that the frequencies corresponded to peaks of the acoustic spectrum under different wavelength were the same, but they were differernt in different diameter of graphite.